Collimation assembly for an imaging device

ABSTRACT

A collimation assembly includes a body, at least four light sources, and at least four collimation lenses. The body has inner surfaces that define at least four hollow portions extending through the body between opposed first and second sides thereof, each hollow portion having opposed first and second openings at the first and second sides of the body, respectively. Each light source is disposed at the first opening of one of the at least four hollow portions and controllable to emit a light beam therethrough. Each collimation lens is disposed at the second opening of one of the at least four hollow portions to receive the light beam emitted by the light source disposed at the first opening and diverge the light beam as the light beam passes through the collimation lens. The at least four light sources and the at least four collimation lenses are supported by the body.

CROSS REFERENCES TO RELATED APPLICATIONS

This application claims priority as a continuation of U.S. patentapplication Ser. No. 14/869,155, filed Sep. 29, 2015.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

None.

REFERENCE TO SEQUENTIAL LISTING, ETC.

None.

BACKGROUND

1. Field of the Disclosure

The present disclosure relates generally to an optical scanning systemin an imaging apparatus, and more particularly to a compact collimationassembly incorporating multiple light sources and collimation lenses foruse in over-filled scanner (OFS) scanning system.

2. Description of the Related Art

In various imaging devices which utilize light to form images, opticalscanning systems are typically incorporated to scan light beams from oneor more light sources onto a target image plane surface. In anelectrophotographic imaging device, for example, the image plane surfaceis typically a photosensitive member. Generally, light beams are sweptacross the image plane surface by a scanning mirror to form light spotsupon the image plane surface along a scan line direction. Commonly usedscanning mirrors include rotating polygon mirrors which scan light beamsin one direction.

A polygon mirror can have either an under-filled or over-filled facetdesign. In an under-filled design, the facet length is significantlywider than the incident light beam width such that the beam footprint ona facet never crosses over the edges of the facet from start to end of ascan line operation. On the other hand, an over-filled design has afacet length that is narrower than the incident light beam such that thebeam footprint on a facet completely fills the facet and extends beyondits edges over the duration of a scan line operation. In this case, thewidth of the laser beam after it is reflected by the polygon mirror isdetermined by the size of the polygon facet.

Generally, in order to have a decent optical performance particularly onlaser spot size, the width of a light beam striking a polygon facet mustbe at least some requisite value, such as 4 mm. By comparison, for agiven number of polygon facets, the under-filled design would require alarger polygon diameter since size of a facet would have to be widerthan the requisite beam width, while the over-filled design wouldrequire a smaller polygon diameter since length of a facet only needs tobe at least the same as the requisite beam width. Thus, scanning systemsthat employ polygon mirrors with larger number of facets can beimplemented at lower costs using the overfilled design. In addition,polygon mirrors having smaller diameters are not only significantly lessexpensive, but also run faster, have less acoustic noise andcontamination on the polygon facets, and allows faster time to firstprint.

In color imaging systems, one of the challenges of having an over-filledfacet design is to achieve a sufficiently wide incoming beam withrelatively small wavefront error for good beam quality for all fourcolor channels. In some existing approaches, beam expanding optic setshave been used to expand laser beams along a scan direction. As anexample, FIGS. 1A-1B illustrate an optical layout of a known scanningsystem 10 employing an over-filled polygon facet design. FIG. 1A is topview of the optical layout of scanning system 10 and FIG. 1B is a sideview thereof. It is noted that prescan mirrors have been removed in FIG.1B to more clearly illustrate the tracing of beams. Four light beams 15from four light sources 20, each for a different color channel, arecollimated through four collimation lenses 25 so that each light beam 15propagates with a constant beam shape and size. After passing throughcollimation lenses 25, the four light beams 15 are received byrespective prescan mirrors 30 and combined to share the same downstreamprescan optics before reaching a polygon mirror 35, as shown in FIG. 1A,while remaining separated along the cross-scan direction 40 as shown inFIG. 1B. The downstream prescan optics include four prescan lenses45A-45D, and two additional prescan mirrors 50A, 50B. First prescan lens45A and third prescan lens 45C are cylindrical lenses with optical poweralong the cross-scan axis to converge the four light beams 15 along thecross scan direction 40. In order to expand each light beam 15 aftercollimation lenses 25, second prescan lens 45B typically has a sphericalconcave surface so as to diverge each light beam 15 along a scandirection perpendicular to the cross-scan direction 40. Meanwhile,fourth prescan lens 45D is a cylindrical lens with optical power alongthe scan axis so as to collimate and slightly converge each light beam15 along the scan direction. Accordingly, each light beam 15 arrives atpolygon mirror 35 with a sufficient beam width that overfills a facet ofpolygon mirror 35 as shown in FIG. 1A.

However, in the example design illustrated in FIGS. 1A-1B, the opticallayout includes a relatively large number of optical components whichpresents added complexity and cost to the scanning system 10. Moreover,the design requiring six prescan mirrors 30, 50 and four prescan lenses45A-45D before the light beam reaches the polygon mirror 35 reducesrobustness of the scanning system. This is because optical performanceof a scanning system is generally very sensitive to alignment of theoptics upstream of the scanning mirror. By having a larger number ofoptical components before the scanning mirror, additional accumulatedtolerances are introduced on the optical path which makes it difficultto have precise optical alignment. Additionally, in order to maintainalignment accuracy, most of the prescan mirrors 30, 50 have mechanicalfeatures to allow for tilt angle adjustments along both scan andcross-scan directions which may not only add more cost but also reducethe overall system robustness.

SUMMARY

Example embodiments of the present disclosure provide an over-filledtype scanning system that utilizes a collimation assembly which improvesrobustness and cost efficiency. In one example embodiment, thecollimation assembly includes a body, at least four light sources, andat least four collimation lenses. The body has inner surfaces thatdefine at least four hollow portions extending through the body betweenopposed first and second sides thereof, each hollow portion havingopposed first and second openings at the first and second sides of thebody, respectively. Each light source is disposed at the first openingof one of the at least four hollow portions and controllable to emit alight beam therethrough. Each collimation lens is disposed at the secondopening of one of the at least four hollow portions to receive the lightbeam emitted by the light source disposed at the first opening anddiverge the light beam as the light beam passes through the collimationlens. The at least four light sources and the at least four collimationlenses are supported by the body.

In another example embodiment, a scanning system includes a housing, ascanning member disposed within the housing and having a plurality ofreflective surfaces, and a collimation assembly disposed within thehousing. The collimation assembly includes a body having inner surfacesthat define a first, a second, a third, and a fourth hollow portionextending through the body between opposed first and second sidesthereof, each hollow portion having opposed first and second openings atthe first and second sides of the body, respectively. A first lightsource, a second light source, a third light source, and a fourth lightsource are positioned at the first openings of the first, second, third,and fourth hollow portions, respectively, the first, second, third, andfourth light sources and controllable to emit first, second, third, andfourth light beams, respectively. A first, a second, a third, and afourth collimation lens are disposed at the second openings of thefirst, second, third, and fourth hollow portions, respectively, thefirst, second, third, and fourth collimation lens for receiving thelight beams emitted by the first, second, third, and fourth lightsources, respectively, and diverging the light beams so as to beincident on at least two reflective surfaces of the scanning member uponarriving thereat.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned and other features and advantages of the disclosedembodiments, and the manner of attaining them, will become more apparentand will be better understood by reference to the following descriptionof the disclosed embodiments in conjunction with the accompanyingdrawings, wherein:

FIGS. 1A and 1B illustrate top and side views, respectively, of a priorart optical layout of a scanning system.

FIG. 2 is a side elevational view of an image forming device accordingto an example embodiment.

FIG. 3 illustrates a laser scanning unit of the image forming device inFIG. 2 including a collimation assembly according to an exampleembodiment.

FIGS. 4A and 4B illustrate top and side views, respectively, of anoptical layout of the laser scanning unit in FIG. 3 according to anexample embodiment.

FIGS. 5A and 5B are a front view and a side cross-sectional view,respectively, with the side cross-section view taken along lines 5B-5Bof FIG. 5A, illustrating a profile of a collimation lens in thecollimation assembly of FIG. 3, according to an example embodiment.

FIG. 6 is a schematic diagram illustrating relative positions of thecollimating lens and a light source of the collimation assembly of FIG.3, according to an example embodiment.

FIG. 7 is a side perspective view of the collimation assembly in FIG. 3showing a front side thereof.

FIG. 8 is a side perspective view of the collimation assembly showing arear side thereof.

FIG. 9 is an exploded perspective view of the collimation assembly inFIG. 7.

FIG. 10 is a rear perspective view of the collimation assembly in FIG.7.

FIG. 11 is a cross-sectional view of the collimation assembly takenalong lines 11-11 of FIG. 7.

FIG. 12 is a front view of the collimation assembly of FIG. 7.

FIG. 13 illustrates a front view of a collimation assembly, according toanother example embodiment.

FIG. 14 illustrates a front view of a collimation assembly, according toanother example embodiment.

FIG. 15 illustrates a front view of a collimation assembly, according toanother example embodiment.

DETAILED DESCRIPTION

It is to be understood that the present disclosure is not limited in itsapplication to the details of construction and the arrangement ofcomponents set forth in the following description or illustrated in thedrawings. The present disclosure is capable of other embodiments and ofbeing practiced or of being carried out in various ways. Also, it is tobe understood that the phraseology and terminology used herein is forthe purpose of description and should not be regarded as limiting. Theuse of “including,” “comprising,” or “having” and variations thereofherein is meant to encompass the items listed thereafter and equivalentsthereof as well as additional items. Unless limited otherwise, the terms“connected,” “coupled,” and “mounted,” and variations thereof herein areused broadly and encompass direct and indirect connections, couplings,and mountings. In addition, the terms “connected” and “coupled” andvariations thereof are not restricted to physical or mechanicalconnections or couplings.

Spatially relative terms such as “top”, “bottom”, “front”, “back” and“side”, “above”, “under”, “below”, “lower”, “over”, “upper”, and thelike, are used for ease of description to explain the positioning of oneelement relative to a second element. Terms such as “first”, “second”,and the like, are used to describe various elements, regions, sections,etc. and are not intended to be limiting. Further, the terms “a” and“an” herein do not denote a limitation of quantity, but rather denotethe presence of at least one of the referenced item.

Furthermore, and as described in subsequent paragraphs, the specificconfigurations illustrated in the drawings are intended to exemplifyembodiments of the disclosure and that other alternative configurationsare possible.

Reference will now be made in detail to the example embodiments, asillustrated in the accompanying drawings. Whenever possible, the samereference numerals will be used throughout the drawings to refer to thesame or like parts.

FIG. 2 illustrates a color image forming device 100 according to anexample embodiment. Image forming device 100 includes a first tonertransfer area 102 having four developer units 104 that substantiallyextend from one end of image forming device 100 to an opposed endthereof. Developer units 104 are disposed along an intermediate transfermember (ITM) 106. Each developer unit 104 holds a different color toner.The developer units 104 may be aligned in order relative to thedirection of the ITM 106 indicated by the arrows in FIG. 2, with theyellow developer unit 104Y being the most upstream, followed by cyandeveloper unit 104C, magenta developer unit 104M, and black developerunit 104K being the most downstream along ITM 106.

Each developer unit 104 is operably connected to a toner reservoir 108for receiving toner for use in a printing operation. Each tonerreservoir 108 is controlled to supply toner as needed to itscorresponding developer unit 104. Each developer unit 104 is associatedwith a photoconductive member 110 that receives toner therefrom duringtoner development to form a toned image thereon. Each photoconductivemember 110 is paired with a transfer member 112 for use in transferringtoner to ITM 106 at first transfer area 102.

During color image formation, the surface of each photoconductive member110 is charged to a specified voltage, such as −800 volts, for example.At least one laser beam LB from a printhead or laser scanning unit (LSU)130 is directed to the surface of each photoconductive member 110 anddischarges those areas it contacts to form a latent image thereon. Inone embodiment, areas on the photoconductive member 110 illuminated bythe laser beam LB are discharged to approximately −100 volts. Thedeveloper unit 104 then transfers toner to photoconductive member 110 toform a toner image thereon. The toner is attracted to the areas of thesurface of photoconductive member 110 that are discharged by the laserbeam LB from LSU 130.

ITM 106 is disposed adjacent to each of developer unit 104. In thisembodiment, ITM 106 is formed as an endless belt disposed about a driveroller and other rollers. During image forming operations, ITM 106 movespast photoconductive members 110 in a clockwise direction as viewed inFIG. 2. One or more of photoconductive members 110 applies its tonerimage in its respective color to ITM 106. For mono-color images, a tonerimage is applied from a single photoconductive member 110K. Formulti-color images, toner images are applied from two or morephotoconductive members 110. In one embodiment, a positive voltage fieldformed in part by transfer member 112 attracts the toner image from theassociated photoconductive member 110 to the surface of moving ITM 106.

ITM 106 rotates and collects the one or more toner images from the oneor more developer units 104 and then conveys the one or more tonerimages to a media sheet at a second transfer area 114. Second transferarea 114 includes a second transfer nip formed between at least oneback-up roller 116 and a second transfer roller 118.

Fuser assembly 120 is disposed downstream of second transfer area 114and receives media sheets with the unfused toner images superposedthereon. In general terms, fuser assembly 120 applies heat and pressureto the media sheets in order to fuse toner thereto. After leaving fuserassembly 120, a media sheet is either deposited into output media area122 or enters duplex media path 124 for transport to second transferarea 114 for imaging on a second surface of the media sheet.

Image forming device 100 is depicted in FIG. 2 as a color laser printerin which toner is transferred to a media sheet in a two step operation.Alternatively, image forming device 100 may be a color laser printer inwhich toner is transferred to a media sheet in a single stepprocess—from photoconductive members 110 directly to a media sheet.Further, image forming device 100 may be part of a multi-functionproduct having, among other things, an image scanner for scanningprinted sheets.

Image forming device 100 further includes a controller 135 and memory137 communicatively coupled thereto. Though not shown in FIG. 2,controller 135 may be coupled to components and modules in image formingdevice 100 for controlling same. For instance, controller 135 may becoupled to toner reservoirs 108, developer units 104, photoconductivemembers 110, fuser 120 and/or LSU 130 as well as to motors (not shown)for imparting motion thereto. It is understood that controller 135 maybe implemented as any number of controllers and/or processors forsuitably controlling image forming device 100 to perform, among otherfunctions, printing operations.

Referring now to FIG. 3, a perspective view of LSU 130 is shownaccording to an example embodiment of the present disclosure. LSU 130includes a collimation assembly 140, pre-scan optics 160, scanningdevice 170, and post-scan optics 180 disposed within a housing 132.

Collimation assembly 140 is generally used to generate light beams foruse in forming a latent image on the surface of photoconductive members110. In one example embodiment, collimation assembly 140 combinesmultiple light sources and multiple collimation lenses into one singleunit, as will be discussed in greater detail below. In the exampleshown, four light beams LB are generated each corresponding to one ofthe cyan, magenta, yellow, and black color image planes. LSU 130 mayalso include driver circuitry (not shown) communicatively coupled tocontroller 135 for receiving video/image information and/or control datathat may be utilized to set and/or vary the laser power used by eachlight source of collimation assembly 140 in order to modulate lightbeams LB.

Pre-scan optics 160 includes a prescan mirror 162 that directs lightbeams LB from collimation assembly 140 to scanning device 170, andprescan lenses 164A, 164B which focus the modulated light beams LB intoscanning device 170. Prescan lens 164A is disposed along the opticalpaths of light beams LB between collimation assembly 140 and prescanmirror 162, while prescan lens 164B is disposed along the optical pathsof light beams LB between prescan mirror 162 and scanning device 170. Inone example embodiment, prescan lenses 164A, 164B may be adhesivelymounted within LSU 130 with a precision fixture and without the need ofadditional metal clips and mounting hardware providing manual positionaladjustment.

Scanning device 170 includes a polygon mirror 172 having a plurality ofreflective surfaces or facets 174 for receiving and reflecting lightincident thereon. In the example shown, polygon mirror 172 is a 12-facetpolygon. Polygon mirror 172 is controllable by controller 135 using amotor (not shown) to rotate at a rotational velocity during an imagingoperation so as to unidirectionally scan at least portions of laserbeams LB in a scan direction 176 to create scan lines on respectivephotoconductive members 110 in a forward direction. As used herein,“scan direction” or “scan axis” refers to a direction across an opticalcomponent that is traversed by a light beam. In some cases, the scandirection may correspond to a direction along the length of an opticalcomponent. On the other hand, “cross-scan direction” or “cross-scanaxis” refers to a direction along the optical component that isperpendicular to the scan direction. The cross-scan direction may, insome cases, correspond to a direction along the height of an opticalcomponent.

Post-scan optics 180 includes a post-scan lens 182 used to focus thelight beams LB and a plurality of mirrors 184A-184D used to direct eachmodulated light beam LB to its corresponding photoconductive member 110.Although FIG. 3 illustrates the use of a single post-scan lens 182, itwill be appreciated that more than one post-scan lens may be used tofocus light beams LB deflected by scanning device 170 into small anduniform spot sizes on the surface of photoconductive members 110. Forexample, four post-can lenses, such as F2 lenses (not shown), may eachbe disposed downstream of respective mirrors 184A-184D at an exit window(not shown) of housing 132 to aid in focusing light beam LB on thesurface of its corresponding photoconductive member 110.

During an imaging operation, image data corresponding to an image to beprinted is converted by controller 135 into laser modulation data. Thelaser modulation data is utilized by the driver circuitry so that LSU130 outputs modulated laser beams LB. According to example embodimentsof the present disclosure, LSU 130 utilizes an over-filled polygon facetdesign. More particularly, each laser beam LB is expanded so as toover-fill a facet 174 of polygon mirror 172 when performing a scan lineoperation. Thus, the width of the light beams LB upon being incident onpolygon mirror 172 is larger than the length of a facet 174 of polygonmirror 172.

With reference to FIGS. 4A and 4B, top and side optical schematiclayouts are illustrated, respectively, showing collimation assembly 140,pre-scan optics 160, and polygon mirror 172 of LSU 130. It is noted thatprescan mirror 162 has been omitted in FIG. 4B to more clearlyillustrate the beam tracings. Collimation assembly 140 includes lightsources 142Y, 142C, 142M, and 142K which emit respective light beams LB,and collimation lenses 144Y, 144C, 144M, and 144K which receive lightbeams LB emitted by corresponding light sources 142Y, 142C, 142M, and142K, respectively. According to one example embodiment, light sources142Y, 142C, 142M, 142K are arranged offset from each other along thecross-scan direction 178 (the cross-scan direction 178 may,alternatively, be seen to be either into or out of the sheet on whichFIG. 4A appears). Each light source 142 may be implemented, for example,using a laser diode or any other suitable device for generating a beamof light. In one example embodiment, each collimation lens 144 expandsand/or diverges the light beam LB received from light source 142 with apredefined divergence angle instead of collimating the laser beam LB.Prescan lens 164A may be a cylindrical lens with optical power along thecross-scan direction 178 so as to converge all four light beams LB alongthe cross scan axis into polygon mirror 172, as shown in FIG. 4B. Forexample, prescan lens 164A may have a light incident surface 165 with aradius of curvature between about 20 mm and about 300 mm. Meanwhile,prescan lens 164B may be a cylindrical lens with optical power along thescan axis so as to converge the laser beams LB along the scan direction176 into polygon mirror 172, as shown in FIG. 4A. As an example, foreach light beam LB, the beam width may be about 5 mm wide along the scanaxis immediately after the light beam LB exits collimation lens 144. Asthe light beam LB continues to diverge after exiting collimation lens144, the beam width may expand to about 10 mm wide before it passesthrough prescan lens 164B. Prescan lens 164B may then converge the lightbeam LB so as to be incident on at least two facets of polygon mirror172. In FIG. 4A, each light beam LB has a beam width BW that is wideenough to be incident on polygon mirror 172 to completely fill or coverat least two facets 174 of polygon mirror 172.

When polygon mirror 172 rotates in the counter-clockwise direction 179,and as a facet 174 exposed to light beams LB rotates between a start andan end of a scan line operation, the width of each laser beam LB atpolygon mirror 172 allows each laser beam LB to cover an entire lengthof the facet from the start to the end of the scan line operation,thereby deflecting only a portion of each incoming light beam LB towardsphotoconductive member 110 during the entire scan line operation.Meanwhile, adjacent facet(s) or portions thereof exposed to light beamsLB at the same time may direct other portions of laser beam LBs awayfrom photoconductive members 110. After the scan line operation, asubsequent scan line operation may be immediately performed by asubsequent facet in the same manner as the preceding facet. Thus,portions of the light beams LB are always on the facet and there issubstantially no inactive scan time corresponding to the time it takesfor light beams LB to cross over an edge of a facet to a next facet fora subsequent scan line operation, thereby allowing for duty cycles(ratio of the active scan time on the photoconductive member to thetotal scan time of a facet) to be very close to 100%.

Because each collimation lens 144 is intentionally designed to divergethe light beam LB passing therethrough, a relatively small diameter maybe used for each collimation lens 144 and all four collimation lenses144 may be stacked relative to each other into one compact unit orassembly, such as collimation assembly 140. In one example embodiment,each collimation lens 144 may have a diameter D between about 5 mm andabout 12 mm, such as about 6.5 mm. By stacking all four collimationlenses 144 and combining them with all four light sources 142 into onecompact collimation assembly 140, a single prescan mirror 162 can beused to receive and direct all four light beams LB to scanning device170. Accordingly, the number of prescan mirrors may be reduced to onecompared to the example design illustrated in FIG. 1A which requiresfour different prescan mirrors 30 separately receiving light beams fromfour collimation lenses 25 and directing the light beams to downstreamoptical components. Prescan mirror 162 may be mounted on an adjustablemount, with adjustable tilt angles along both scan and cross-scan axes.

In one example embodiment, the profile of each collimation lens 144 maybe adjusted so as to intentionally cause laser beam LB to divergeinstead of being collimated after passing through collimation lens 144.FIGS. 5A, 5B, and 6 show an example shape and profile of collimationlens 144, in accordance with example embodiments of the presentdisclosure. FIG. 5A illustrates a front view of collimation lens 144while FIG. 5B illustrates a side cross-sectional view thereof takenalong lines 5B-5B of FIG. 5A. Collimation lenses of this type are theones disclosed in U.S. patent application Ser. No. 14/140,979, filedDec. 26, 2013, entitled “Optical Scanning System and Imaging Apparatusfor Using Same” and assigned to the assignee of the present application.The content of such patent application is hereby incorporated herein byreference in its entirety.

As shown, collimation lens 144 may include a generally concave lightincident surface 146 upon which light beam LB is received from lightsource 142, and a generally convex light exit surface 148 upon whichlight beam LB exits collimation lens 144. In an example embodiment,light incident surface 146 may be spherical while light exit surface 148may be aspheric. The concave shape of the light incident surface 146 andthe convex shape of the light exit surface 148 allow collimation lens144 to intentionally diverge laser beam LB towards polygon mirror 172,instead of collimating light beam LB. In other alternative exampleembodiments, collimation lens 144 may have a light incident surface thatis generally convex or substantially flat or planar that would allowcollimation lens 144 to diverge and/or expand laser beams passingtherethrough.

In another example embodiment, relative positions between collimationlens 144 and corresponding light source 142 may be adjusted such thatthe distance between them is less than a focal length of collimationlens 144. FIG. 6 illustrates an example arrangement between light source142 and collimation lens 144. As shown, collimation lens 144 has anoptical axis 150 and a focal point 152 therealong. Normally, positioninglight source 142 at focal point 152 would cause laser beam LB emitted bylight source 142 to collimate upon exiting collimation lens 144.However, in this example embodiment, light source 142 is arranged alongoptical axis 150 but offset from the focal point 152 of collimation lens144 and, more particularly, between collimation lens 144 and its focalpoint 152. Thus, collimation lens 144 is positioned from light source142 at a distance less than its focal length so that light beam LB woulddiverge instead of collimate after exiting light exit surface 146 ofcollimation lens 144.

FIGS. 7-12 show collimation assembly 140 according to exampleembodiments of the present disclosure. Collimation assembly 140, asillustrated, includes light sources 142 and collimation lenses 144maintained in a body 200. Body 200 has a front side 203, a rear side206, and inner surfaces 209 defining hollow portions 212 formed throughbody 200 and extending between opposed front side 203 and rear side 206.Body 200 further includes openings 213 each for receiving a respectivefastener (not shown) for attaching collimation assembly 140 to datumsurfaces of LSU 130. In one example embodiment, body 200 may be formedas a single molded piece. Each hollow portion 212 defines a firstopening 215 at the front side 203 and a second opening 218 at the rearside 206. The light sources 142 are disposed and retained in therespective second openings 218 while collimation lenses 144 are disposedat the respective first openings 215 such that each collimation lens 144is positioned along the beam axis 221 (FIG. 9) of a respective lightsource 142. As seen in FIGS. 10 and 11, each of the second openings 218at the rear side 206 of body 200 is formed with a pocket 224 sized toreceive a light source 142. In one example embodiment, light sources 142may be retained in their respective pockets 224 by an adhesive or otherretaining means. Each light source 142 includes lead wires 143 which areconnected to the driver circuitry for receiving pulse signals forpowering the light source 142.

Collimation assembly 140 further includes a plurality of support members227 extending from the front side 203 of body 200, and a plate member230 disposed between the front side 203 and collimation lenses 144.Support members 227 may be integrally molded as part of body 200 orformed as separate components that are attached to the front side 203 ofbody 200. Support members 227 extend through plate member 230 viacorresponding slots 233 formed on plate member 230 and are positioned tosupport collimation lenses 144 in a substantially linear or stackedarrangement. In the example shown, four support members 227 engage withthe circumferential edge of a collimation lens 144 and position thecollimation lens 144 along the beam axis 221 of the respective lightsource 142. Installing a collimation lens 144 may be accomplished, forexample, by precisely aligning the collimation lens 144 along the x, yand z directions relative to the corresponding light source 142, andadhesively attaching the collimation lens 144 to four support members227 surrounding the corresponding aperture 236 such as by usingultraviolet (UV) adhesive. It will also be appreciated that differentshapes, sizes, and/or arrangements of support members 227 may be usedother than those depicted in the illustrated examples.

A plurality of apertures 236 are formed along a centerline 239 of platemember 230. In the example shown, the apertures 236 are formed with arectangular shape and are located between the collimation lenses 144 andrespective first openings 215 to allow portions of the light beams LBemitted by light sources 142 to pass through the plate member 230 and bereceived by respective collimation lenses 144. Each aperture 236 may besized to have a height that allows sufficient amount of optical energyto pass through for forming a latent image on photoconductive member 110while preventing or reducing stray light from one light source 142 frombeing imaged into the collimation lens associated with an adjacent lightsource 142 to prevent optical “cross-talk” between image informationsignals of two adjacent light beams LB, and a width that allows laserbeam LB, after passing through collimation lens 144 and prescan lenses164A, 164B, to have a beam width that overfills at least two facets 174of polygon mirror 172 upon arriving thereat. In one example embodiment,aperture 236 may have a height between about 0.3 mm and about 3 mm, anda width between about 2 mm and about 12 mm. In other alternative exampleembodiments, other shapes for apertures 236 may be used.

Adjacent collimation lenses 144 may be spaced relatively close to eachother so as to reduce the height H of collimation assembly 140 and allowfor a relatively small space requirement within LSU 130, whichconsequently allows for the size of LSU 130 to be reduced. In oneexample embodiment, the spacing between the centers of adjacentcollimation lenses 144 may at least correspond to the diameter of eachcollimation lens 144, such as between about 5 mm and about 12 mm. As anexample, in FIG. 12, centers of adjacent collimation lenses 144 incollimation assembly 140 are spaced at a distance d that is greater thanthe diameter D of collimation lenses 144 such that adjacent collimationlenses 144 are arranged linearly (or centers of the collimation lenses144 are arranged along a line) but vertically spaced from each other bya gap G. In one example embodiment, gap G may be between about 0.2 mmand about 5 mm. In another example embodiment illustrated in FIG. 13,centers of adjacent collimation lenses 144 in collimation assembly 140 ₁are spaced at a distance d′ that is substantially equal to the diameterD of collimation lenses 144 such that adjacent collimation lenses 144are arranged so that the centers thereof are arranged along a linewithout spacing therebetween. In this way, height H of collimationassembly 140 may be further reduced to height H₁ by reducing the gapbetween adjacent collimation lenses 144 to approach zero or actually bezero such that the outer circumferential surface of adjacent collimationlenses 144 contact each other.

In another example embodiment, height H of collimation assembly 140 maybe further reduced by cutting out segments of each collimation lens 144.For example, in FIGS. 14-15, each collimation lens 144′ is cut alongchords of its circumference to remove opposed upper and lower segmentsthereof and form opposed edge surfaces 154A, 154B. In one exampleembodiment, the cut segments of collimation lens 144′ may, combined,correspond to up to about 50 percent of the front surface area thereof.When collimation lenses 144′ are stacked with cut-edge surfaces 154A,154B arranged parallel to each other and extending in a directionperpendicular to the linear arrangement of collimation lenses 144′, areduced height of collimation assembly 140 may be achieved. In FIG. 14,cut-edge surfaces 154A, 154B of adjacent collimation lenses 144′ arespaced from each other by a gap G resulting in collimation assembly 140₂ having reduced height H₂. In FIG. 15, adjacent collimation lenses 144′are arranged such that substantially no gap exists between adjacentcut-edge surfaces 154A, 154B resulting in collimation assembly 140 ₃having a further reduced height H₃. Thus, by cutting away upper andlower segments of each collimation lens 144, the arrangement ofcollimation lenses 144 can be made more compact and the height of thecollimation assembly can be further reduced.

With the above example embodiments, LSU 130 utilizes a compactcollimation assembly 140 which incorporates all four light sources 142and four collimation lenses 144. Additionally, stacking andincorporating the light sources 142 and collimation lenses 144 into onecollimation assembly 140 eliminates the need to employ separate prescanmirrors 30 as illustrated in FIG. 1A. Instead, a single prescan mirror162 can be used to receive and direct all four light beams LB toscanning device 170. Further, utilizing collimation lenses 144 aseffective beam expanding optical components eliminates the need toincorporate additional beam expanding optics in LSU 130. Accordingly,use of collimation assembly 140 and its compact design allows for asimplified optical design which not only provides significantly lessnumber of optical components, which can reduce the tolerance stack upcaused by accumulated variation of size and/or position of individualdownstream optical components and improve robustness, but also providessignificant savings with respect to the overall cost of LSU 130, andconsequently the cost of imaging forming device 100.

The description of the details of the example embodiments have beendescribed in the context of electrophotographic imaging devices.However, it will be appreciated that the teachings and concepts providedherein are applicable to other systems employing optical scanners forscanning light beams. Additionally, although the collimation assembly inthe above example embodiments has been described as having four lightsources and four collimation lenses at opposed openings of four hollowportions of the body, it will be understood that having more than fourhollow portions of the body, more than four light sources and more thanfour collimation lenses may be implemented for the collimation assembly.

The foregoing description of several methods and an embodiment of theinvention have been presented for purposes of illustration. It is notintended to be exhaustive or to limit the invention to the precise stepsand/or forms disclosed, and obviously many modifications and variationsare possible in light of the above teaching. It is intended that thescope of the invention be defined by the claims appended hereto.

What is claimed is:
 1. A collimation assembly, comprising: a body havinginner surfaces that define a plurality of hollow portions extendingthrough the body for passing beams of light; a plurality of lightsources on first sides of the plurality of hollow portions; and aplurality of collimation lenses on second sides of the plurality ofhollow portions opposite the first sides, wherein the body is orientedupright during use such that the plurality of light sources arevertically stacked above one another as are the plurality of collimationlenses vertically stacked above one another.
 2. The collimation assemblyof claim 1, wherein the body is a unitary body.
 3. The collimationassembly of claim 1, wherein the plurality of light sources are linearlyarranged.
 4. The collimation assembly of claim 1, wherein the pluralityof collimation lenses are linearly arranged.
 5. The collimation assemblyof claim 1, wherein there are four said light sources.
 6. Thecollimation assembly of claim 1, wherein there are four said collimationlenses.
 7. The collimation assembly of claim 1, further including aplate member between the body and the plurality of collimation lenses.8. The collimation assembly of claim 7, wherein the plate memberincludes apertures to pass only a portion of the beams of light fromrespective ones of the plurality of light sources to respective ones ofthe plurality of collimation lenses.
 9. The collimation assembly ofclaim 7, wherein the body further includes support members to engagecircumferential edges of the plurality of collimation lenses and thesupport members pass through the plate member.
 10. A collimationassembly for use in an imaging apparatus, comprising: a unitary bodyhaving inner surfaces that define a plurality of hollow portionsextending through the body for passing beams of light; four lightsources supported by the unitary body on first sides of the plurality ofhollow portions; and four collimation lenses supported by the unitarybody on second sides of the plurality of hollow portions opposite thefirst sides, wherein the unitary body is oriented upright during use inthe imaging apparatus such that the four light sources are verticallystacked above one another as are the four collimation lenses verticallystacked above one another.
 11. The collimation assembly of claim 10,wherein the unitary body defines a single molded piece.
 12. Thecollimation assembly of claim 10, further including a plate memberbetween the unitary body and the four collimation lenses.
 13. Thecollimation assembly of claim 12, wherein the plate member includesapertures to pass only a portion of the beams of light from respectiveones of the four light sources to respective ones of the fourcollimation lenses.
 14. The collimation assembly of claim 12, whereinthe unitary body further includes support members to engagecircumferential edges of the four collimation lenses and the supportmembers pass through the plate member.
 15. An imaging apparatus,comprising: a housing; a collimation assembly in the housing, thecollimation assembly having a body having inner surfaces that definefour hollow portions extending through the body for respectively passingfour beams of light; four light sources on first sides of the pluralityof hollow portions; and four collimation lenses on second sides of theplurality of hollow portions opposite the first sides, wherein the bodyis oriented during use such that the four light sources are stackedabove one another as are the four collimation lenses stacked above oneanother; and a single mirror in an optical path immediately after thecollimation assembly that exclusively reflects all said four beams oflight.
 16. The imaging apparatus of claim 15, further including fourphotoconductive members each defining a light beam scan direction, thefour light sources being offset from one another in a cross-scandirection substantially perpendicular to the light beam scan direction.17. The imaging apparatus of claim 15, further including a plate memberbetween the body and the four collimation lenses.
 18. The imagingapparatus of claim 17, wherein the plate member includes apertures topass only a portion of the four beams of light from respective ones ofthe four light sources to respective ones of the four collimationlenses.
 19. The imaging apparatus of claim 17, wherein the body furtherincludes support members to engage circumferential edges of the fourcollimation lenses and the support members pass through the platemember.
 20. The imaging apparatus of claim 15, further including one ormore polygon mirrors configured to receive the four beams of light fromthe single mirror.